1. Field of the Invention
The invention lies in the field of recovering silver from cuprous chloride by amalgamation techniques.
2. Description of the Prior Art
In the recovery of copper from its ores, particularly sulfide ores, it is well known, as disclosed in U.S. Pat. Nos. 3,785,944 and 3,972,711, in order to avoid the disadvantages of recovering copper electrolytically, pyrometallurgically, and by other methods, to solubilize the copper in the ore as cuprous chloride in a leach followed by cooling the slurry to crystallize the cuprous chloride and recover copper from the cuprous chloride crystals. A major disadvantage of wet recovery like this technique, is that impurities like silver, iron and others are carried over during the crystallization into the cuprous chloride crystals and end up as impurities in the final copper product. Some of these impurities are deleterious to the properties of copper and reduce its sale value. While the latter may not be necessarily true of silver, the failure to recover the high priced silver so that it is not sold along with the copper at the price of copper, detracts from the economic feasibility of the overall process.
In accordance with prior art, silver is removed from high chloride solution by cementation on copper metal. It was found that the presence of cuprous copper in the solution however renders this technique inoperative. For example, it was found that silver was efficiently removed by cementation with copper metal down to &lt;0.001 g/l Ag from 200 g/l NACl or 182 g/l Fe.sup.++ from solutions containing no Cu.sup.+. Also that the presence of 11, 23, or 30 g/l Cu.sup.+ in these solutions only permitted the Ag concentration to be lowered to 0.009, 0.016, and 0.026 g/l Ag, respectively. These data illustrate the deleterous effect of Cu.sup.+ and therefore demonstrate the need for a reductant which can cement Ag but not cement Cu.sup.+ from the solution.
Accordingly, it is an object of this invention to provide an effective process for recovering silver from cuprous chloride and additionally produce a silver and iron-free cuprous chloride.
It is another object of this invention to provide an improvement in the process for recovering copper from its ores in which the copper is solubilized as cuprous chloride, the cuprous chloride crystallized and the copper produced from the cuprous chloride crystals, the improvement being a procedure for recovering silver from the cuprous chloride crystals before copper is produced from them.